SOLD: HeadRoom Desktop Balanced Amplifier w/ Built-in DAC
Will Ship To: Anywhere
SOLD: HeadRoom's Balanced Desktop Amp.
MINT Condition. I'm the original and only owner. Light usage - roughly 4-6 hours on most weekends for about 2 1/2 years. This is truly the Swiss Army Knife of high end headphone audio. Hook up several sources (digital and analog) and experiment to your heart's content. Great for balanced drive....also great for hooking up two different headphones simultaneously for A-B comparisons. This has been the heart of home rig - so it's been very well cared for. I generally had it set up with simultaneous connections to:
-Balanced analog output from any balanced CD player
-Optical (Toslink) output from a small footprint transport
-USB output from my laptop for Pandora
-Coax output from a digital iPod doc
I love just sitting there and switching back and forth between various inputs and drive modes (SE vs Balanced). I learned a TON about sampling rates and high res audio using this great little tool.
-Built-in, sweet-sounding digital-to-analog converter (DAC)
-Class-A-biased amplifier section
-Switching-mode power supply
-Brick-shaped SMPS "Brick" can deliver 1.35 amperes
Cirrus Logic's 24bit/192kHz, 120 dB Digital to Analog Converter. It is isolated and tightly regulated. In the analog section of the DAC are found two high quality Burr-Brown 134, single package Op-Amps, with only discrete metal thin-film resistors and poly-phenylenesulfide (poly-film) capacitors nearby.
Home Module Upgrade
The Home Module consists of two pair of 4-layer circuit boards (one each for the left and right channel) that are connected with a series of header pins used to solder the module to the main circuit board. This module is designed to sound great without going up the ridiculously steep part of the diminishing returns curve. The output current amplifier is our version of the highly regarded Diamond Buffer discrete transistor design by Walt Jung. internal input buffer, crossfeed, summer, and gain stage use the Burr-Brown OPA2134 op-amp. All these active circuits are forced into class "A" bias with constant current sources. Resistors are 1% metal thin-film, and caps in the signal chain are poly-phenylenesulfide (poly film). The sound of this module is not only well balanced and punchy, it's also liquid and integrated.
Stepped Attenuator Upgrade
Standard HeadRoom amps come with a damn good Alps pot. But due to industrial process, though it sounds and tracks very well, there are spots at some settings where there just has to be a little unevenness between the loudness of the channels, and (over time) a little layer of particulate matter accumulates on the wipers due to numerous passes over the plastic conductive element. Such imperfections are eliminated by using a stepped attenuator instead, which is "simply a multi-pole switch that allows you to select one of a series of resistors to adjust the volume."
Edited by khatch - 11/23/10 at 3:09pm